The invention relates to an air intake system for an internal combustion engine of a motor vehicle.
German patent application no. DE 196 13 860 discloses an air intake filter unit for a motor vehicle engine, which has an unfiltered space that is connected to intake lines with a main intake and a secondary intake. Furthermore, a closing device is provided, which can alternately close one intake line and open the other intake line. This closing device is moved by an actuating element such that the closing device closes the main intake and opens the secondary intake if the motor vehicle dips into water. This actuating element is operatively linked with a slide valve. The slide valve is arranged inside a pipe open at its lower end and is sealed with respect to said pipe. The slide valve is operatively linked with a permanent magnet. The closing device is operatively linked with an additional permanent magnet. The permanent magnet of the closing device is rotatably arranged in relation to the permanent magnet of the actuating element.
The drawback in this device is the substantial amount of space required for the pipe, which is arranged in the engine compartment. The pipe cannot be designed too small since otherwise the changeover point of the arrangement cannot be exactly defined. Furthermore, this mechanical switching arrangement responds only if the vehicle dips into standing water. Road spray does not cause sufficient pressure to be built up for switching, so that water can get into the intake system and impair engine function.
It is an object of the invention to provide an intake system that can be integrated into a small installation space.
Another object of the invention is to provide an air intake system which can prevent entry of snow, road spray or splashes of water into the intake tract.
These and other objects are achieved by the invention as described and claimed hereinafter.
The intake system according to the invention for an internal combustion engine of a motor vehicle has a first unfiltered air intake and a second unfiltered air intake. The two unfiltered air intakes are combined into a common line, which communicates with the internal combustion engine. The two unfiltered air intakes may also be joined directly in front of the internal combustion engine, so that each unfiltered air intake has its own components, e.g., its own filter element. Each unfiltered air intake consists of an opening through which air can flow into the intake system, and a line segment, which connects said opening with the line. The unfiltered air intakes can be sealed by one or several sealing elements, so that the air will flow either through the first unfiltered air intake or through the second unfiltered air intake into the line communicating with the internal combustion engine. The sealing element seals the respective air intake completely, so that air can flow into the line only through the unsealed unfiltered air intake. The sealing element can, for instance, be formed by a rotary body provided with corresponding openings. This rotary body unblocks the first unfiltered air intake in one end position and seals the first unfiltered air intake in a second end position.
The line communicating with the internal combustion engine guides the inflowing air either directly or indirectly to the internal combustion engine. If the air is indirectly guided to the internal combustion engine, the air can be pretreated, e.g., dried or cooled. If the air is directly guided to the internal combustion engine, no further component is required in the line.
The first unfiltered air intake is arranged in the motor vehicle at a location that is advantageous for air intake. A preferred location is the front area, since the air is pressed into the unfiltered air intake as a function of the vehicle speed, which improves the filling ratio of the cylinders. Furthermore, the air sucked into the front area is cooler than the air present in the engine compartment. In the front area, however, snow, ice, road spray and splashes or gushes of water can get into the first unfiltered air intake. Road spray is defined as air mixed with water droplets of any size. Road spray can, for instance, be splashed up from the road by a vehicle traveling ahead or be produced by rain. The term floodwater describes a larger amount of water, which occurs, for example, in the form of a surge when a river is crossed. The second unfiltered air intake is arranged at a location in the motor vehicle, which is unfavorable for air intake but is protected from road spray and splashes or gushes of water. Preferred locations for arranging this second unfiltered air intake can for instance be the engine compartment or the ventilation system.
To actuate the sealing element or valve member, an actuator is provided, which is connected to a control element. This actuating mechanism can, for instance, be an electric motor or a vacuum unit and can be actuated by means of the control element. The actuator executes a rotary or linear movement, which moves the sealing element into an end position and thereby either seals the first or the second unfiltered air intake. The control element is formed by a moisture sensor, which is equipped with a signal output to control the actuating mechanism. The moisture sensor can of course also be used for control.
The moisture sensor can be adjusted in such a way that it emits a signal to the actuating mechanism even in the presence of road spray, which already impairs the function of the internal combustion engine. This signal causes the first unfiltered air intake to be closed. In another adjustment of the moisture sensor, the signal to close the first unfiltered air intake is emitted only if the moisture sensor is surrounded by water. The signal of the moisture sensor can be transmitted to the actuating mechanism either directly or via an electronic unit, e.g., the engine control. As soon as the first unfiltered air intake is sealed by the sealing element, the second unfiltered air intake is opened, so that the internal combustion engine receives combustion air that is sucked in through the second unfiltered air intake.
In one advantageous embodiment of the invention, the valve member is a flap. The flap may, for instance, be circular, oval or rectangular, so that it blocks the second unfiltered air intake in a first position and the first unfiltered air intake in a second position. The flap may be arranged centrally on a flap shaft and moved by a rotary motion of the flap shaft. In other embodiments, the flap shaft is arranged in an edge area and thus permits an unfiltered air intake without interfering contours. To prevent water from penetrating into the first unfiltered air intake, particularly in case of immersion into a body of water, the flap may be provided with a circumferential seal. Also feasible are embodiments in which a first flap is arranged in the first unfiltered air intake and a second flap in the second unfiltered air intake, said two flaps communicating with one another. As soon as the first flap changes its position, the second flap is also moved, so that one unfiltered air intake is always open while the other unfiltered air intake is closed. The flaps can communicate mechanically, e.g., by means of a strut, or electronically by means of a signal emitted particularly by the moisture sensor.
According to one specific embodiment, the flap has two flap parts correspondingly connected with one another. These flap parts can be arranged at a defined angle contacting one another directly or they can be rigidly connected by means of connecting elements. A parallel mutual arrangement of the flap parts represents a special embodiment. However, the flap parts can also be spatially separate from one another so that they correspond with one another only via the actuating mechanism. The flap parts can, for instance, have a circular, oval or rectangular cross section, with one flap part sealing one unfiltered air intake. The flap parts can have a circumferential seal, by means of which the unfiltered air intakes can be tightly closed. If flap parts are used to seal the unfiltered air intakes, said unfiltered air intakes can open out into the common line in a variety of ways.
In another advantageous embodiment, the actuating mechanism is a lifting magnet, which communicates with the moisture sensor. The lifting magnet can execute an axial or a radial movement to move the sealing element. As soon as the moisture sensor detects water, it sends a signal to the lifting magnet causing a movement of the lifting magnet and thus a change in position of the sealing element. The lifting magnet responds to the signal within a few fractions of a second, so that the first unfiltered air intake is sealed before water can penetrate and reach the internal combustion engine. As is well known, lifting magnets have an armature, a spring, a coil, a yoke and an electrical connection.
In another specific embodiment of the invention, the moisture sensor is arranged in the same plane as the first unfiltered air intake. It may be arranged at a point remote from the unfiltered air intake, which primarily comes into contact with water. The sealing element is disposed above the moisture sensor at a defined distance to allow sufficient response time between detection of water and closing of the first unfiltered air intake so that no water can penetrate. Preferably, the moisture sensor is arranged at a location within the engine compartment. This causes the moisture sensor to detect the environmental conditions inside the engine compartment. During travel through water, the moisture sensor dips into the standing water at the same time as the unfiltered air intake and immediately causes the first unfiltered air intake to be closed by the sealing element, which is arranged at a higher level. Arranging the moisture sensor in the same plane as the first unfiltered air intake makes it possible to prevent a premature closure of the first unfiltered air intake, which would occur if the moisture sensor were arranged on a lower level.
Another embodiment of the invention provides that the moisture sensor is arranged in the first unfiltered air intake. The moisture sensor thus detects precisely the conditions prevailing in the first unfiltered air intake. It causes the first unfiltered air intake to be closed by the sealing element as soon as water penetrates into the first unfiltered air intake. The sealing element is arranged downstream from the moisture sensor. The distance between the sealing element and the moisture sensor is selected in such a way that once water has been detected, there is still sufficient response time to seal the first unfiltered air intake before the water flows past the sealing element and reaches the internal combustion engine. By arranging the moisture sensor in the first unfiltered air intake, said first unfiltered air intake is closed only if water actually enters the first unfiltered air intake. In other words, the air is sucked in through the first unfiltered air intake, which is more favorable for the internal combustion engine, and only if water actually penetrates into the first unfiltered air intake, the first unfiltered air intake is closed and the air is sucked in through the second unfiltered air intake.
According to another advantageous embodiment of the invention, the moisture sensor can be heated. For example, resistance heating can be used for this purpose. It is also feasible, however, to use the heat from adjacent components to heat the moisture sensor. By heating the moisture sensor it is possible, for example, to melt any snow or ice. Heating the moisture sensor can also be used to evaporate any adhering water droplets.
An advantageous embodiment of the invention provides for a moisture sensor that is configured as a conductivity sensor with two electrodes. When the electrodes come into contact with water, the conductivity of the sensor changes. The configuration of the conductivity sensor, particularly the distance between the electrodes, should be selected as a function of the switching conditions, i.e., when the first unfiltered air intake should be closed and when the second unfiltered air intake should be opened. The smaller the distance between the electrodes, the sooner the electrodes are connected, for instance, by a single drop of water. This causes the conductivity sensor to emit a signal and the actuating mechanism to close the first unfiltered air intake. If the distance between the electrodes is large, a single water drop is not sufficient to connect the electrodes. Only after both electrodes have for instance been submerged in a ford, the conductivity sensor emits the signal to close the first unfiltered air intake. In one embodiment, the conductivity sensor is, for example, equipped with two electrodes, which are separated by an insulating layer consisting, for example, of air, plastic or ceramic. As soon as there is water on the insulating layer, which bridges said layer, the electrodes are conductively connected with one another, whereby the sensor signal is generated and the sealing element is moved to its second position by means of the actuating mechanism. Depending on how wide the insulating layer is, the moisture sensor responds either to individual droplets in case of road spray or only when the electrodes are completely surrounded by water, in case of splashes or floodwater.
It is advantageous that the moisture sensor is formed by at least two electrically conductive wires, which are spaced at a distance from one another. The electrically conductive wires are made of a material that has little electrical resistance and is thus a good electrical conductor, e.g., metals or metal alloys. The wires, which are spaced at a distance from one another, can extend parallel or at an angle to one another.
According to a further embodiment of the invention, the electrically conductive wires are applied to a substrate. They may be embedded in the substrate or be supported on the substrate. The substrate is made of a material that insulates the conductive wires when dry. This material can be made water absorbent and then becomes electrically conductive. In another embodiment of the substrate, the substrate material is not water absorbent, so that the water is deposited in the form of droplets on the substrate. Such a water droplet bridges the electrically insulating substrate material and connects the wires so that a current flow is created, which causes the first unfiltered air intake to be closed.
In another embodiment of the invention, the moisture sensor is a capacitance sensor with two capacitor plates spaced at a distance from one another. The capacitor plates are connected to an AC voltage source, so that an electrical field with a defined field strength is produced. The field strength, as is well known, is a function of the applied voltage and the distance between the capacitor plates. The farther apart the capacitor plates are spaced from one another the weaker the electrical field. The capacity of the capacitors is a function of the area and the distance between the capacitor plates as well as the relative permittivity of the material between the capacitor plates.
The capacitor plates are made of an electrically conductive material, e.g., metal. This electrically conductive material may be provided with a protective layer of a non-conductive material, e.g., synthetic resin material. The protective layer can, for instance, serve for corrosion protection and enclose the capacitor plates completely, so that the capacitor plates do not come into direct contact with water or air. The capacitor plates are connected to an evaluator unit in which the electrical field between the capacitor plates is evaluated. The evaluator unit measures the capacity of the capacitor plates with a high-frequency AC voltage. The relative permittivity of air equals approximately 1 while that of water is approximately 80. As soon as water instead of air is sucked in, the relative permittivity between the capacitor plates is substantially changed. This causes the evaluator unit to send a signal to the actuating mechanism and the first unfiltered air intake to be closed by the valve member.
The capacitance sensor can be adjusted in such a way that it responds only to floodwater, i.e., only to a substantial change in the relative permittivity between the capacitor plates. In another adjustment, a slight change in the relative permittivity can already be sufficient to close the first unfiltered air intake.
The capacitor plates can be arranged at any location in the vehicle, either parallel or in mirror image to one another. In preferred embodiments, the capacitance sensor is arranged on the first unfiltered air intake. The capacitor plates are semicircular and can enclose the first unfiltered air intake. With a capacitance sensor, the medium being sucked in can be reliably determined. In addition, capacitance sensors are insensitive to dirt.
In another advantageous embodiment of the invention, the capacitance sensor has a concentric configuration. The capacitor plates are cylindrical, with an outer capacitor plate surrounding an inner capacitor plate. This concentrically configured capacitance sensor can be disposed directly in the first unfiltered air intake, where the contour of the outer capacitor plate corresponds to the inner contour of the first unfiltered air intake. To fix the inner capacitor plate within the outer capacitor plate, one or several segments may be provided. These segments affect the flow of the intake air only to a very minor extent. Furthermore, the segments can be made of an electrically insulating material, particularly the same material as the protective layer of the capacitor plates. Using a concentric configuration of the capacitance sensor creates a stable field between the capacitor plates, so that the capacitance sensor is not susceptible to interference.
In a further embodiment of the capacitance sensor, the capacitor plates extend within the first unfiltered air intake at an angle to one another. Each capacitor plate on the one hand contacts the first line segment and on the other hand is centrally fixed inside the first unfiltered air segment. In this embodiment, the angle is preferably 90xc2x0. As a result, four electrical fields are produced and evaluated.
One advantageous embodiment of the invention provides for the arrangement of several moisture sensors. For instance, two identical moisture sensors may be provided, which may be arranged at different locations inside the engine compartment. A switching logic can thereby be established. Furthermore, moisture sensors with different modes of action or sensitivities may be combined. The moisture sensors may be arranged directly side by side or in different locations on the vehicle. In one possible arrangement, a highly sensitive moisture sensor is disposed in the first unfiltered air intake and a less sensitive moisture sensor in the engine compartment below the first unfiltered air intake. This makes it possible to configure different switching variants. As soon as the less sensitive moisture sensor is submerged in water, it can emit a signal to close the first unfiltered air channel, even though the highly sensitive moisture sensor has not yet made contact with water. In a further variant, both moisture sensors come into contact with road spray, whereby the less sensitive moisture sensor does not yet emit a signal, but the highly sensitive moisture sensor emits the signal to close the sealing element.
It is advantageous if the operability of the moisture sensor can be tested upon start of the internal combustion engine. As soon as the engine is started, a sensor test checks the operability of the moisture sensor to ensure that the moisture sensor will actually work when required. To display the status of the moisture sensor to the operator of the internal combustion engine, the moisture sensor can be connected, for example, to an indicator light. If the sensor works properly the light is extinguished after the sensor test is completed. If the sensor test is negative, i.e., the moisture sensor does not work as specified, the indicator light may blink or be on continuously. This informs the operator that the intake system does not operate properly and that the first unfiltered air intake may not close in case of water, so that travel through water should be avoided and the intake system should be repaired as soon as possible.
In a specific embodiment of the inventive concept, the operability of the actuating mechanism and the sealing element can be checked upon start of the internal combustion engine. The actuating mechanism and the sealing element are moved each time the internal combustion engine is started to ensure that all parts are operable when required and have not been frozen, e.g., due to corrosion. Testing of the actuating mechanism and the sealing element can be indicated, for instance, by means of a control indicator, such as a warning light, which is extinguished only after successful movement.
These and other features of preferred embodiments of the invention, in addition to being set forth in the claims, are also disclosed in the specification and/or the drawings, and the individual features each may be implemented in embodiments of the invention either alone or in the form of subcombinations of two or more features and can be applied to other fields of use and may constitute advantageous, separately protectable constructions for which protection is also claimed.